Variable speed transmission



Jlme 25, 1940. c. E. HENRloD, FlLs 2,205,832

mamma srEEn 'musursgzon Filed June 2. 1937 3 Sheets-Sheet 2 I zal?? d M:g4-h

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k N ai CIM/6 50004930 HEIV/WOD, FILS June 259 14940..

C. E. HENRIOD. FILA-S VARIABLE SPEED TRANSMISSION I 3 Sheets-Sheet 3Filed June 2. 1937 Patented June 25, 1940 UNITED STATES PATENT OFFICE-Application June 2,1937, Serial No. 146,057 In Luxemburg March l?, 1937The present invention relates to variable speed transmissions, and it isespecially, although not exclusively, concerned with transmissions ofthis kind used in connection with automobile vehicles.

The object of the present invention is to provide a device of this kindwhich is simpler, more emcient, and better capable of meeting therequlrements, of practice .than transmissions as used at the'presenttime.

According to the essential feature of the presi ent invention, I controlthe bringing into or out of action of the two lower gear combinationsthrough distinct automatic clutches, respectively, and I make use, forthe upper gear combinations, of ajsupplementary automatic clutch,preferably provided at the rear of the gear box, and which is arrangedin such manner that, when it is let in, it can transmit to the automaticclutch corresponding to the second gear combination, the reactionproduced by the resisting torque, in such manner as to produce theautomatic disengagement of this last mentioned clutch and to bring -intoplay a third gear combination, which may correspond either to areduction gear ratio or to direct drive, as long as the resisting torqueremains greater than the driving torque, and to. produce the automaticengagement of saidlast mentioned clutch, as soon as both torques balanceeach other, which permits of obtaining a fourth gear combination, whichmay correspond either to direct drive or to a step-up gear ratio.

Other features of the present inventionwill result from the followingdetailed description oi some speciiic embodiments thereof.

Preferred embodiments of the present invention will be hereinafterdescribed, with" reference to the accompanyingl drawings, given merelyby 4o way of example, and in which:

Fig. 1 is an axial sectional view of a. variable speed and automaticcontrol transmission made according to a first embodiment` of thepresent invention; 4

Figs. la and 1b are perspective views showing the mounting of the massesaccording to the invention. 5 Fig. 2 is a similar view'oi' an analogbustransmission made accordingto a second embodiment of the invention;

Fig. 3 is a sectional view, partly (left hand side) on the line A--B ofFig. 2, and partly (right .hand side) on the line C-D of Fig. 2;

Fig. 4 is a radial sectional part view onthe line E-F of Fig. 3;

(Cl. 'M -337) 'respectively to the drive of the driven shaft 5 lothrough the iirst and second gear combinations.l For the sake ofsimplicity, I will rst describev the structure and operation of clutch 4corresponding to the second speed. I provide, on either side of thefriction disc 4, two annular 15 plates 6' and 1, the plate designated byreference number 6 being rigid with fly-wheel 2 by means of bolts (notshown) and the other being supported by balls or the like 8 housed incircular and tapered recesses 9 provided in the adjacent 2o faces ofsaid annular plates 6 and 'I, said balls being distributed at regularintervals from one another and serving chiefly to establish thedrivingvconnection betweensaidv plates 6 and 1. In' the circumferentialdirection, the Walls of these 25 grooves 9 are so inclined that therelative anglilar displacement of annular plate I with respect to plate6 causes said annular plates to be moved away from each other,`and-therefore disengages clutch 4. The engagement of the clutchelements is obtained (as described more specifically in connection withFig. 3) through masses Ill en` gaged with a suitable play in radialhousings 39' (Fig. 1a) provided in theperipheral portions of the annularplates and acting thereon,.under the 85 iniiuence of the centrifugalforce, through balls or the like Il cooperating with the inclined wallsof circular and tapered recesses provided in said annular plates, saidmasses I0 actingin opposition to the action of balls 8. Y 40 'Ihisspecic type'of clutch does not constitute a feature of the invention andit might be re- -placed by' any other gradual coupling device.

The automatic clutch corresponding to -the rst speed includes annularplatesl 'I and I3, lo- 45 cated on either side of the friction disc 3.

q annular plates E, 'I and I3 are connected in rota- Vso tion by massesI4 and plates 'l and by balls 9, plate 6 being rigid with flywheel 2 andwith the driving shaft I, so that masses Il) and |41 are subjectedsimultaneously to the action of the centrifugal force. These masses aredevised Ain such manner as to produce first the gradual engagement ofclutch 3 (corresponding to the first speed) the latter being fullyengaged for a given speed of the engine.

VAs `a consequence of this engagement, the motive power is transmittedthrough' disc 3 to a sleeve I6 keyed tov disc 3 and freely rotatablecoaxially with an auxiliary shaft Il, itself free to rotate and coaxialwith respect to the driven shaft 5. This sleeve I6 carries a gear I8constantly in mesh with a toothed wheel I9 keyed on an intermediateshaft 2|. Wheel I9 drives,

'through a free-wheel device 20, a sleeve 38, and

on this sleeve there is keyed an axially slidable pinion 22 controlledfrom a distance through a forked rod 23 or any other equivalent means.

This sliding pinion 22 is adapted to occupy any of 'three characteristicpositions, to wit: a median position for bringing the transmission intoneutral, a left hand side position (that shown by the drawing)corresponding to all forward speeds, and a right hand side position forreverse gear in which said pinion drives, through a reversing gear, notshown, the gear wheel 2d that corresponds to reverse gear. l

Wnen the sliding pinion is in its position corresponding to forwardspeeds, it is in meshwith aV gear wheel 25 mounted, by means of afreewheel device 26, -on a sleeve 21, frcely rotatable coaxially onauxiliary shaft I1, whereon is keyed a plate 28 belonging to a clutchdevice provided at the rear of the gear box and the function of whichwill be hereinafter explained.

'Ihis clutch device is intended to bring into play the third and thefourth gear combinations, the latter corresponding to direct drive. Itincludesfriction elements 29,'(either single or dou-- ble) carried by acentral disc 30 integral'with the auxiliary shaft |1. On either side ofthese friction elements 29, there are clutch plates 28 and 3|, adaptedto cooperate with centrifugall masses 32 and balls 33 and 39 in a manneranalogous to that above described with reference to the first clutch,balls 39 serving chiefly to estab- `lish the driving connection betweenplates 28` Plate 3| drives, through a cylindrical clutch element withinternal teeth 34, a central toothed disc or plate 35 keyed on thedrivenV shaft 5.

.wheel 31 rigid with sleeve 38.

These driving means might be replaced by a flexible driving disc. V

Sliding pinion 22 having been brought by forked rod 23 into vits forwardspeed position, in which it is in mesh with gear wheel 25, if the engineis caused to speed up, clutch 3 is gradually applied through the effectof centrifugal masses It and against the action of springs I2. When thespeed of the engine has become sufficiently high, the driven shaft 9 iscaused to work in first gear through clutch 3, sleeve IE, gears IB andI9, free-wheel device 20,- sleeve 39', gear wheels 22 and 29, sleeve 21,plate 2B, balls 39, plate 3| and couplingmeans 3ft-35. When thiscombination is working, clutches l and 29 are disengaged becausethe'centrifugal force acting on masses I0 and 32 is not sufficient forproducing their radial displacement to an amplitude suiiicient forengaging the annular friction'discs with the intermediate frictionelements.

If the engine is further accelerated, I obtain the engagement of thecooperating parts of clutch t and movement is then transmitted throughvthis clutch to the auxiliaryshaft .I1 which carries a pinion 36constantly in mesh with a toothed It follows that the sliding pinion 22is driven with a gearA ratio corresponding to second speed. During thisdrive, clutch 3 remains in engagement and lthe gear wheels I6 and I9 ofthe first gear combination remain in mesh without this involving anydrawback, owing to the-presence of free-wheel device 20. On the`contrary, the rear clutch 29 remains in inoperative position because thespeed of shaft 5 transmitted to centrifugal masses 32 through the partsbrought into play by the second speed combination is not yet sufficientfor bringing said clutch into action.

When the engine is still furtherV accelerated, the speed isv obtainedfor which the third gear combination becomes possible or necessary andfor which the automatic engagement of the rear clutch 29 is obtained. Itfollows that the'centrai disc 30 and the auxiliary shaft I1 areangularly coupled' with the plates 28 and 3| of this,

the action of the driving shaft. As annular disc i 6 is rigid withfly-wheel and is continuously driven by it, only annular disc .1 canundergo the elect of this reaction, which results in an angulardisplacement of annular disc 1 with respect to annular disc 6 (thismovement being .made possible by the lateral play provided in thehousings of the centrifugal masses I0 and in the circular and taperedrecesses of balls II). It follows that balls -8, which cooperate withthe sloping walls of recesses 9, move annular discs 6 and 1 awayA fromeach other, against the action of centrifugal masses |0, and causelclutch 4 to be disengaged, whereby the element d of this clutch andauxiliary shaft I1 cease tol be driven by the driving shaft I. On thecontrary, clutches 3 and 29 remain in operative posion.

I thus obtain the third gear, through clutch 3, sleeve IB, gear WheelsI8 and I9, free wheel device 29, gear wheels 31 and 36, auxiliary shaftIl, central disc 3D, clutch 29 and driven shaft 5. The toothed wheels22-25 (which were brought into play for the rst and second speeds)remain in mesh although they turn at a dierent relaquence of thebalancing op the driving torque and the resisting torque, the effect ofthe centrifugal masses I predominates on that of balls 8 and l thelatter are pushed back towards the bottom of their recessesY 8 in suchmanner that automatic clutch 4 is again in engagement. In this case themovement is transmitted in direct drive because the clutches 3, 4 and 29are all in engagementand the relative movements between certain rotaryelements of the gear box are rendered possible by the presence offree-wheel devices 20 and 26.

, It is obvious that `the switching to-lower gear combinations isobtained automatically through vthe same control means and under theinfluence.

reversing gear (not visible in the drawing) so that the latter can drivetoothed wheel 24,'keyed on sleeve 21 under the sam conditions as aboveexplained for the (drive in rst gear.

In the embodiment illustrated by Figs. 2 to 5,

the positions of clutches I and II, corresponding respectively to thefirst and the second gear combinations, are inversed. In other words,the clutch I, corresponding to the vfirst speed, is located close to thefly-wheel 2 driven by the engine, and its friction disc 3 is keyed onthe central auxiliary shaft I'I. On the contrary,the friction disc 4 ofthe clutch II corresponding to the second speed is mounted on sleeve I6,freely engaged on the central shaft Il.

Furthermore, instead of making use of distinct centrifugal masses (suchas I4 and I0 in the embodiment just above described) for controllingthese two clutches respectively, I make use of common centrifugal masses|01, which work in the following manner:

`Masses |01 (for instance there are three of them, as visible on theright hand side of Fig. 3) are engaged with a certain play in housings39' provided in annular plates I3, 'I andl 6 between which the frictiondiscs 3 and 4 are provided, and they extend axially over the whole ofthese three annular plates.` Annular plate 6, which belongs to clutchII, is fixed to fly-wheel 2.- As in the preceding embodiment, annularplate 6 drives annular plate 1 through balls of the like 8 housed intapered recesses 9 (Fig. 5) forming inclined and 1 of clutch l1.

Masses |01, which extend axially over the three annular plates I3, 'Iand 6, bear upon the external sides of plates I3 and 8 through balls II1housed in circular' and tapered recesses, the contour of which'ls wellshown on Fig.- 3. I'he size of the balls II1 and the shape of therecesses are such that when the balls are at the deepest ends thereof,springs I2 and 4I move plates I 3-1 and 1-6 away from one anotherrespectively and from the corresponding friction discs 3 and 4. In thisposition, clutches I and II are disengaged. When the speed of the engineincreases from the idling speed, the centrifugal force tends to moveoutwardly masses |01, which turn together with flywheel 2, andA I obtainiirst the compression of springs I2 and the gradual engagement of clutchI, which `causes shaft 5 to be driven in first speed through the gearshereinafter described. As disc 3 is connected to shaft I1 on which theresisting torque acts, and'as the plate I of clutch I also belongs toclutch II by being connected to plate 6 through balls 8, the latter,under the effect of the resisting torque, move from the deepest ends oftheir recesses (which corresponds to a slight angular displacement ofplates 1 and 6). It follows that plates 6 and I are positively movedaway from friction disc 4, so that clutch II remains disengaged untii,as a consequence of the increase of the engine speed, the centrifugalforce has become sufhcient for bringing back balls 8 to the bottom oftheir recesses (while .compressing springs 4|). At this'time, both ofthe clutches I and II are in operation, and the drive is effected insecond speed through means as will be hereinafter described.

Clutch III, preferably located at the rear of the gear box, and which isreserved for the two upper speeds, is arranged in a manner analogous tothat above 'described with reference to Fig. l.

It .includes centrifugal masses 32 acting through preceding example, butthrough a. disc or platewith flexible blades 351, which is rivetedonshaft 5 and the ends of which blades are engaged 1n notches 42provided in ,the periphery of pl te 3l.

` The function of this ,clutch III is however di erent from that aboveindicated for the analogous clutch of the embodiment of Fig. 1.

When the engine is running at idling speed, the three clutches I, 1I,III are disengaged under the effect 'of their respective springs..`among which only springs I2 and 4I are vi ible on the drawing.

The centrifugal masses |01 d 32 are still inoper-l ative and the balls 8and 39 are at the bottoms of their respective recesses.

When the speed of the engine is increased, the

centrifugal masses |01, as above explained, gradually cause the platesI3 and -1 of clutch I to move toward each other, and the driving poweris transmitted to the driven shaft through fly-wheel 2,

plate 6, balls 8, plates I and I3, friction disc 3,

central shaft I1. a free-wheel ,device 43 riveted on said shaft, andpinion 44, freely mounted on shaft I1. This pinion 44 meshes with-atoothed wheel 45 rivetted on a sleeve 38 freely mounted on anintermediate shaft 2|. This sleeve 2| also carried a toothed wheel 46 inmesh with a gear 41 provided with a free-wheel device 48 through whichthe movement is transmitted to a sleeve 49 carrying the plate 28 ofclutch lII. The transmission of movement then takes place through balls39, plate 3i, plate 351 with its flexibleblades, and nally shaft 5,which is thus driven in iirst speed. It should be noted that, while thisoperation is takingplace, the two free-wheel devices 43 and 48 actpositively in the drive and the action of the resisting torque on plates6 and l, which serve to the transmission' of the driving force, producesan angular displacement of these plates with respect to each other, insuch manner that balls 8 leave the bottoms of their recesses,

and prevent engagement of the parts of clutch II. The same occurs forplates 28 and 3i of clutch III, for which the centrifugal masses 32 Thetransmission of the driving force is theneiected through clutch II, bymeans of itsA friction disc e, to sleeve l5, which drives the couple ofgear wheels 58 and 5i, the last mentioned gear i being keyed on sleevet, which is freely engaged.) on the intermediate shaft 2l. The movementis then transmitted through parts 4t, 41, 48, 4Q, 28, 38 and 851, to thedriven lshaft E, which is driven in second speed.' It should be notedthat during -this operation, onlyv free wheel 48 acts in a positivemanner in the drive. The presence of free wheel device 43 is necessaryfor permitting toothed wheels 44. and 45 (corresponding to first speed)to remain in mesh :and clutch I to remain in engaged position.

When the speed of the engine furtherv in creases, either because itsworking is accelerated or because the resisting torque decreases, therecomes a time when the centrifugal masses 32 of clutch IIIbecome capableof forcing back balls 39 into their respective recesses, lwhich producesthe automatic engagement of the parts of clutch III. The characteristicsof clutch II (importance of masses 01, size and shape of balls 8 and ofthe corresponding recesses or grooves) have however been calculated insuch manner that the reaction of the resisting torque, which is nowtransmitted through clutch III which has Just been brought into' play,becomes suilicient for producing the automatic disengagement of clutchII, whereas clutch I'remains inoperative position. Under theseconditions, the transmission*` friction disc 30 of clutch III. As this-clutch is in engaged position, the effortis transmitted through plates28 and 3| to the flexible blade plate 351 and the' driven shaft. Itshould be noted that, during this operation, clutches .I `and m areengaged and clutch II is disengaged, that free-Wheel device 43 workspositively in the drive and free wheel device 48 permits the freerotation of the couple of gears 41 and 48 with which it cooperates, Asthe transmission of the driving force takes place without any speedreduction, the driving shaft i drives the driven shaft 5 in direct drive(third gear combination).

Finally. when, under these conditions, the driving torque becomes higherthan the resisting torque, the engine still accelerates andnthecentrifugal masses lill become capable of bringing back clutch II intooperative position. The transmission of the driving effort i s theneffected through clutch II, its friction disc 4, sleevel |85, the coupleof gear wheels 50 and 5I, sleeve 38, the couple of gear wheels 45 and44, sleeve 52, friction disc 30, keyed at 53 on this sleeve, clutch IIIand the flexible blade plate 351, to the driven shaft. The driving forceis therefore transmitted at an in-v creased speed, through gears 5l and45-4i, to the driven shaft 5 while clutches I, II and III are operativeand free-wheel devices 43 and iii turn freely, thatis to say exert nopositive action in the transmission. i

It is clear that, when the resisting torque increases or when thedriving torque'diminishes for any reason, I-successively obtain thedisengagement of clutch II, which corresponds to passing down to thethird gear combination, or direct drive.v If these workingconditions-are still more accentuated, I automatically obtain thedisengagement of clutch IIIand theengagement of clutch II (second speed)and, nally, the disengagement of clutch II (first speed) before passingto idling speed.

In order to obtain reverse gear, it sumces, as for the example of Fig.1, to slide travelling pinion i6 into position 481 (shown in dottedlines) so as to ybring it into mesh with a reversing gear (not shown inthe drawing) whereby the latter can drive toothed wheel 2t, keyed on asleeve V2l rigid withthe plate 28 of clutch II, under the sameconditions as those indicated for running in rst speed.

With the arrangement above described, I obtain a variable speed andautomatic working transmission which, as well in the case of theembodiment of Fig. 1 as in that of Fig. 2, has the following chiefadvantages over existing transmissions of the same kind:

a. It includes only three clutch devices for a four speed gear box,whereas in known devices, it is generally necessary to make use of fourclutches corresponding respectively to the four gear combinations;

b. It includes a reduced number of gears lower.

than the number of gear elements employed in ordinary four speed boxes;

c. The first and second speed combinations, for which the resistingtorque is very great, work respectively through clutchesI and II merelyintended to transmit the driving torque, whereas clutch -III upon whichthe resisting torque acts, is called 4into play only for the thirdspeed, and for direct drive, in the case of the embodiment of Fig. 1,and for direct drive and a step up gear ratio in the case of theembodiment of Figs. 2 to 5, that is to say under circumstances in whichthe resisting torque is small, which permits of reducing .the weight,and more particularly the radial dimensions, of said clutch;

d. By positioning some of the clutches at the front and some at the rearof the gear box. I reduce the length of the sleeves or other connectionelements' connecting the clutches to the gears to be driven;

e. The free wheels, such 's 20 and 26 (Fig. 1) or 43-and 48 (Figs. 2 to5) necessary for permitting certain relative movements between` theelements of the gear box, are positioned at advan- A tageous points andtheir number is reduced to two for a. four speed gear box;

f. The particularly `simple control of the clutches permits ofconsidering as possible, withthe transmission.

'. In addition, the` variable speed transmission illustrated by Figs. 2to 5 further has the following advantages:

As the thirdI speed is direct drive and the fourth speed corresponds toa step-up transmission, I obtain the advantage that the engine runs 'atrelatively low speed of revolution ,for high speeds of the vehicle,which renders the drive smoother and permits of saving fuel whilereducing wear and tear.4 Furthermore, in cities it is more frequently`possible to run with direct drive.

The automatic bringing into 4or out of action of the step-up gearcombination, under the combined influences of the speed of the vehicleand the resisting torque is obtained through the simultaneous engagementof the three clutches I, II and III, whereas, for direct drive, only twoclutches, to wit I and III are in operation. Clutch III is directlyconnected to the wheels of the vehicle and remains in operation. whenrunningin direct drive and with 'a step-up gear combination, whichensures a. safe working thereof and simplifiesl its construction `andits adjustment since its state undergoes no modification at high speeds.i

It should be noted that thetransmlssion of the driving power takesplace, when in direct drive, through ifree-wheel device 48, which ispositively brought into play for this operation but which turns freelywhen runningwith the step-up gear combination.'

Futhermore, by arranging the -clutches Vand the4 gear wheels of thetransmission as vshown by Figs. 2 to 5, I can dispose the step-up gears5KB-5i ahead ofthe gear box, so that they can be driven directly by theengine and through clutch II. v, Y f

In a general manner, while I have, in the above description, disclosedwhat I deemy to'be practical andeicient embodiments of the presentinvention, it should` be well understood that I do not Wish to belimited thereto as thereV might be changes made in the arrangement,disposition and -form of the parts Without depart'- ing from theprinciple of the present invention' 1 as comprehended the scope of theappended claims.

What I claim is: Y

l. A variable speed transmission device which comprises, in combination,a driving shaft, a driven shaft, means for unidirectionally couplingsaid driven shaft with said driving shaft with a reduction gear ratio,said means including an automatic clutch responsive to speed variationsof said driving shaft so as` to be yin operative engagement only forvalues of said speed exceeding a predetermined value, means forunidirectionally coupling said driven shaft with said driving shaft witha smaller reduction gear ratio, said last mentioned means including'anautomatic clutchv responsivev to speed variations of said driving shaftso as to 4be in operative engagement 'only for values of said speedexceeding' another andhigher `predetermined value, means,

,Y operative by variations of the difference between values ofesaiddifference exceeding apredetermined value, and afthird clutch,responsive to speed variations of said driven'shaft so as to be inoperative engagement only` for values of said speed exceeding a thirdand still higher predetermined value. said third clutch being'inter-`posed between said driven shaft, on the 'one hand, and on the other handparts of both of said coupling means, including the respective clutchesthereoLYWhereby, according as whether.

the second clutch is inoperative engagement or not, two other higherspeeds are obtained.

l 2.- A variable speed transmission device which lil comprises, incombination, a driving shaft,` a driven shaft, means forunidirectionaily coupling said driven shaft with said driving shaft witha reduction gear ratio, said means including an automatic clutchresponsive lto speed variations of said driving shaft so as to be inoperative engagement only for values of said speed ex- 'ceeding apredetermined value, means for unidirectionally coupling said drivenshaft with said driving shaft with a smaller reduction gear ratio, saidlast mentioned means including an automatic clutch responsive to speedvariations of said driving shaft so as to be in operative engagementonly for values of said speed exceeding another and higher predeterminedvalue means, operative by the difference between the driving torguetransmitted from said driving shaft to said second mentioned clutch and*the` resisting torque transmitted thereto from said driven shaft, fordisengaging said second mentioned clutch when said difference is notzero.

vand a third clutch, responsive to" speed Variations of said drivenshaft so as to be in operative engagement only for values of said speedf, exceeding a third and still higher predetermined value, said thirdclutch being interposed between said driven shaft, on the one hand, and,on the other hand, one of-said two first mentioned clutches directly,andVV a part of the coupling means leading to the other of said two rstmentioned clutches, whereby, according as whether the second mentionedclutch is in operative engagement or not, two other higher speeds areobtained, one of which corresponds to direct drive.

3. A variable speed transmission device which compriseal in combination,a driving shaft, a driven shaft, means for unidirectionaliy couplingsaid driven shaft with said driving shaft with a reduction gear ratio,said means including an automatic clutch responsive to speed variationsof said driving shaft so as to be in operative engagement only forvalues of said speed exceedn ing a predetermined value, means for'unidirectionally coupling said driven shaft with said driving shaftwith a smaller reduction gear ratio,

said last mentioned means including an automatic clutch responsive tospeed 'variations ofv said driving shaft so as to bein operativeengagement only for values of said speed exceeding another and higherpredetermined value, means.

operative by the difference between the drivingl torque transmitted fromsaid driving shaft to said second mentioned lclutch and the resisting. v

thirdclutch being interposed between said driven` y shaft, on the onehand, and, on the other hand,

. both the second mentioned clutch directly and a part ofthe coupling.means between the first mentioned clutch and said driveny shaft,whereby. when the second mentioned clutch is disengaged by the reactionof the resisting torque, a third mentioned clutch is in operativeengagement,

direct drive is obtained.

4'. A variable speed transmission device which comprises, incombination, a driving shaft, a

driven shaft, means for unidirectionally coupling said driven shaft withsaid driving shaft with a reduction gear ratio, said means including anautomatic clutch responsive to speed variations of said driving shaft soas to. be in operative engagement only for values of said speedexceeding a predetermined value, means for unidirectionally couplingsaidy driven shaft with said driving shaft with a smaller reduction gearratio, said last mentioned means including an automatic clutchresponsive tospeedi variations of said driving shaft so as to be inoperative engagement onlyfor va1ues of said speed exceeding another andhigher predetermined value, means, operative by the difference betweenthe driving torque transmitted from said driving shaft to said secondmentioned clutch and the resisting torque transmitted thereto from saiddriven shaft, for disengaging said second mentioned clutch when saiddiierence is not zero, and a third clutch, responsive to speedvariations of said driven shaft so as to be in mentioned clutch isdisengaged by the reaction of the resisting torque, direct drive isobtained; and, when said second mentioned clutch is in operativeengagement, a step-up gear ratio is obtained.

5. An automatic transmission for coupling driving and driven shaftscomprising, rst and second automatic clutches, two gear combina.- tionscontrolled by said clutches and operatively connected to the drivenshaft, means controlled by lower and higher speeds of the driving shaftto engage said two clutches for first and second speeds respectively, athird automatic clutchV operatively connected to the driven shaft, meansresponsive to the speed of the driven shaft and automatically operativewhen the power required by the driven shaft is lower lthan the powerdelivered by the driving shaft to engage said third clutch, said thirdclutch being operatively connected to said second clutch to trans mitthe torque of the driven shaft thereto, means responsive to apredetermined excess of the' power required by the. driven shaftover thepower delivered by the driving ,shaft to disengage said second clutchfor third speed, said last means becoming inoperative when such excessof power drops below said predetermined value to permit said first meansto reengage said second clutch for fourth speed'.

6. A device as claimed in claim 5 in which' .second clutches includes atleast one of said gear combinations.

v. A device as claimed in claim 5, in which said third speed is a directdrive.

, 8. A device as claimed in claim 5, in which said fourth speed is adirect drive.

CHARLES EDOUARD HENRIOD, FILS.

